80 ZAMITES. 



nt least 3-4 ft. in length, and compared with PteropJiyllum 

 Humloldti, Dunk. ; the latter species, however, appears to be a 

 typical PteropJiyllum species, and quite distinct generically from 

 Ettingshausen's type. Schenk reproduces the figure given by 

 Ettingshausen, and points out the fact that none of the pinna 

 apices are shown in the specimens. Very probably we may regard 

 Zamites Gopperti, Schenk, as Z. Buchiamis (Ett.), seen from the 

 lower surface ; Schenk himself compared the former species with 

 Pt&rophyllum saxonicum, Reich., 1 from Mederschunen, and there 

 seems good reason to follow Fontaine in including P. saxonicum, 

 as figured by Ettingshausen, as synonymous with Z. Buchianum. 

 Hosius and von Marck 2 have figured a small fragment of a frond, 

 which they refer to P. saxonicum, but the specimen is too im- 

 perfect to admit of accurate identification. The same authors 

 refer another specimen of cycadean frond to Dioonites abietinus, 

 which shows a distinct resemblance to the smaller forms of Zamites 

 Bitchianus (cf. Hosius and Marck, pi. xliv. fig. 199, and PI. III. 

 Fig. 1 of the present volume), but perhaps the similarity is hardly 

 sufficiently well marked to warrant the inclusion of the fossil in 

 the synonym list of the present species, without the addition of 

 a query. Some writers have preferred Dioonites to Pterophyllum 

 for Ettingshausen's species; Schimper and Fontaine both adopt 

 the former name. The Potomac flora has yielded numerous 

 examples of fronds which Fontaine refers to D. Buchiamis; he 

 speaks of the species as " one of the most widely diffused and 

 characteristic fossils of the Potomac flura." 3 This author institutes 

 two varieties of Ettingshausen's species D. Buchiamis, var. 

 obtusifoliws and var. ang list i foil us. It might perhaps be advisable to 

 adopt Fontaine's terms, and apply them to certain forms of the 

 species represented in the numerous examples from the "Wealden 

 of Ecclesbourne, but there is the usual difficulty to be faced in 

 drawing lines between one form and another. In looking at some 

 specimens we find the pinna apices are very distinctly acutely 

 tapered, and closely correspond with Fontaine's D. Buchiamis var. 

 angustifolius ; but in such a frond as V. 21737, although on the 

 whole the pinnae are tapered, yet some of the segments terminate 



1 Ettingshausen (A. 8), Sitz. k. Ak. "Wiss. Wieii. vol. Iv. Abth. i. pi. i. 

 figs. 11 and 12. 



2 (A. 1), Palontographica, vol. xxvi. p. 213, pi. xliv. fig. 198. 



3 Potomac Flora, p. 182. 



